C#用DataTable实现Group by数据统计

1、用两层循环计算，前提条件是数据已经按分组的列排好序的。

 1 DataTable dt = new DataTable();
 2 dt.Columns.AddRange(new DataColumn[] { new DataColumn("name", typeof(string)),
 3                                         new DataColumn("sex", typeof(string)),
 4                                         new DataColumn("score", typeof(int)) });
 5 dt.Rows.Add(new object[] { "张三","男",1 });
 6 dt.Rows.Add(new object[] { "张三","男",4 });
 7 dt.Rows.Add(new object[] { "李四","男",100 });
 8 dt.Rows.Add(new object[] { "李四","女",90 });
 9 dt.Rows.Add(new object[] { "王五","女",77 });
10 DataTable dtResult = dt.Clone();
11 for (int i = 0; i < dt.Rows.Count; )
12 {
13     DataRow dr = dtResult.NewRow();
14     string name = dt.Rows[i]["name"].ToString();
15     string sex = dt.Rows[i]["sex"].ToString();
16     dr["name"] = name;
17     dr["sex"] = sex;
18     int score = 0;
19     //内层也是循环同一个表，当遇到不同的name时跳出内层循环
20     for (; i < dt.Rows.Count; )
21     {
22         if (name == dt.Rows[i]["name"].ToString()&&name == dt.Rows[i]["sex"].ToString())
23         {
24             score += Convert.ToInt32(dt.Rows[i]["score"]);
25             dr["score"] = score;
26             i++;
27         }
28         else
29         {
30             break;
31         }
32     }
33     dtResult.Rows.Add(dr);
34 }
35 
36 dtResult中的数据即是最终结果。

2、 借助DataTable的Compute方法，DataTable中数据不用事先排好序。

 1 DataTable dt = new DataTable();
 2 dt.Columns.AddRange(new DataColumn[] { new DataColumn("name", typeof(string)),
 3                                          new DataColumn("sex", typeof(string)),
 4                                          new DataColumn("score", typeof(int)) });
 5 dt.Rows.Add(new object[] { "张三","男",1 });
 6 dt.Rows.Add(new object[] { "张三","男",4 });
 7 dt.Rows.Add(new object[] { "李四","男",100 });
 8 dt.Rows.Add(new object[] { "李四","女",90 });
 9 dt.Rows.Add(new object[] { "王五","女",77 });
10 DataTable dtResult = dt.Clone();
11 DataTable dtName = dt.DefaultView.ToTable(true, "name","sex");
12 for (int i = 0; i < dtName.Rows.Count; i++)
13 {
14     DataRow[] rows = dt.Select("name='" + dtName.Rows[i][0] + "' and sex='" + dtName.Rows[i][1] + "'");
15     //temp用来存储筛选出来的数据
16     DataTable temp = dtResult.Clone();
17     foreach (DataRow row in rows)
18     {
19         temp.Rows.Add(row.ItemArray);
20     }
21 
22     DataRow dr = dtResult.NewRow();
23     dr[0] = dtName.Rows[i][0].ToString();
24     dr[1] = temp.Compute("sum(score)", "");
25     dtResult.Rows.Add(dr);
26 }

3、使用linq to DataTable group by实现（引用：System.Linq;   如果Datatabel提示没有AsEnumerable()  则引用 System.Data.DataSetExtensions）

var query = from t in dt.AsEnumerable()
            group t by new { t1 = t.Field<string>("name"), t2 = t.Field<string>("sex") } into m
            select new
            {
                name = m.Key.t1,
                sex = m.Key.t2,
                score = m.Sum(n => n.Field<decimal>("score"))
            };
if (query.ToList().Count > 0)
{
    query.ToList().ForEach(q =>
    {
        Console.WriteLine(q.name + "," + q.sex + "," + q.score);
    });
}

收集整理，非原创。转载：https://www.cnblogs.com/sydeveloper/archive/2013/03/29/2988669.html

posted @ 2021-05-11 15:14  LiuzzBK  阅读(1708)  评论(0)  编辑  收藏  举报